The proposed research will lead to the development of a vaccine that can be used to protect young children against infections caused by Haemophilus influenzae type b (Hib). The vaccine will be based on the pili that facilitate the organism's adherence to the naspharyngeal epithelium. Antibodies produced in response to the vaccine will bind to Hib pili, preventing adherence and colonization, thereby lowering the incidence of systemic infections caused by the organism. In the Phase I feasibility study, we will determine the ability of pili-specific antibodies to block adherence of heterologous Hib strains to epithelial cells in vitro. The main objectives of Phase II will be to determine: (a) whether passively administered antibodies to pili reduce or prevent colonization of model animals and (b) the dose and route of administration needed to stimulate the formation of pili-specific antibodies in the nasopharnyx of immunized animals. This research provides a basis for developing vaccines against Hib and other pathogens that adhere to surfaces by means of pili or adhesin proteins.